Polymer composites are widely utilized in numerous applications, including automotive, home construction, electronic and consumer good products. One frequent requirement of polymer composites in certain applications is that they must be flame retardant. In order to prevent polymers from burning, the propagation of the combustion cycle has to be stopped.
There are various strategies for combating the fire chemically and physically in both the vapor phase and condensed phase. When a polymer breaks down there are many pathways in which the polymer can decompose to form high-energy free radicals. In the vapor phase, the combustion cycle can be stopped by physically diluting the flame with non-combustible gases and chemically capping the high-energy free radicals. In the condensed phase, two methods are generally utilized to stop the combustion: (i) formation of char, which adds a protective layer between the flame front and the polymer fuel, and (ii) dilution of solid fuel with inorganic fillers that decompose to dilute the flame.
The most widely utilized flame retardants on the market today are halogenated flame retardant additives. The halogenated flame retardant retard the flame efficiently by acting quickly as a radical trap that catalytically stops the fire by capping the high-energy free radicals in the vapor phase. This effectively stops the combustion cycle and extinguishes the flame. Halogenated flame retardants, however, may evolve harmful gases and can have a negative effect on the environment. For that reason, other approaches for extinguishing flames in polymeric compounds have been sought.
Conventional flame retardant additives are various organic and inorganic compounds that are blended with commercially available polymers to impart flame retardant properties within the polymer. The conventional additives may employ vapor phase or condensed phase methods for arresting the flames. The addition of conventional flame retardant materials to a polymer composition may adversely impact the physical characteristics of the composition, ultimately rendering the composition unsuitable or undesirable for its intended purpose. Highly filled flame retardant polymers often have inferior physical characteristics compared to competitive materials due to their molecular architecture. Such materials are often incapable of achieving the desired strength and impact characteristics. Other flame retardant compositions offer molecular architecture that potentially limits the subsequent processing once the multi-component composition is created.